1. Field
The present invention relates generally to the field of electrical connectors, and particularly, to a current mode coupler that connects to a current mode data bus.
2. Description of the Related Art
A data communication system on an airplane needs to facilitate data sharing between various subsystems, such as between a navigation subsystem and a flight control subsystem. Currently in use in the industry is a common data bus that connects each of the subsystems, thereby allowing communication between the connected subsystems. A common data bus implementation allows connection between the subsystems and alleviates the need for direct wiring between each subsystem. This solution is more practical in the avionics industry because it reduces the amount of wiring necessary to establish communication between the subsystems, thereby reducing the weight burden of the avionics communication system.
A current mode data bus is typically used in the avionics industry. A current mode data bus communication system utilizes a twisted pair cable to facilitate communication. Each subsystem is electrically connected to the data bus via current mode couplers that sense electrical current in the twisted pair cable.
Various subsystems interface to the current mode data bus without an invasive connection to the wire itself. The non-invasive interface is achieved by electrically connecting the subsystem to the data bus by use of inductive coupling. Inductive coupling is accomplished by including in the electrical connection a magnetic structure that allows for mutual inductance between the data bus cable and the magnetic structure. As long as the twisted pair cable is unshielded, the mutual inductance allows a subsystem to receive and transmit data from and to the data bus without physical connection to the cable itself.
Non-invasive coupling, accomplished by use of a current mode coupler employing mutual inductance, is suitable for several reasons. A communication system designed to allow subsystems to communicate on one data bus requires less wiring, thereby reducing the weight of such a system. The non-invasive nature of the current mode coupler proves to be more easily maintainable, allowing replacement of communication system connectors without undermining the integrity of the data bus by requiring physical connection to the cable wiring.
Current mode couplers currently in use have several disadvantages. Current mode couplers currently used employ an intricate alignment mechanism that is necessitated by the E-core/E-core (EE) structure. The faces of the legs of the E-cores used in an EE structure must be perfectly aligned to reduce signal losses. The minimal surface area available on the E-core faces requires that maximum contact occur between the E-cores; hence, precise alignment is requisite.
In addition, other couplers use separate inactive base sections that contain one set of E-cores and a separate active section that also contains an E-core and additional circuitry.
This configuration requires a low impedance interface between the two sections of the coupler that can be in the form of spring fingers implemented in the upper and lower base attachment. This requirement causes additional weight, component count, and manufacturing cost.
Another disadvantage of conventional current mode couplers is its use of a separate base unit and upper housing. This results in unnecessary weight since the upper housing contains the active electronics, the lower housing (i.e., base unit) contains the inactive electronics, and an inductance equalizer must be established between the two. This configuration requires a low impedance interface between the two sections of the coupler that can be in the form of spring fingers implemented in the upper and lower base attachment. This requirement causes additional weight, component count, and manufacturing cost.
A further disadvantage of conventional current mode couplers is the use off-the-shelf transformers. Off-the-shelf transformers have significant failure modes and the use of the off-the-shelf transformers increases the cost of the current mode coupler.
The current mode coupler disclosed in U.S. Pat. No. 5,241,219 is a non-invasive coupler that creates a magnetic core structure that senses signals on a data bus cable. The patent generally discloses an intricate assembly that requires precise alignment of an upper and lower magnetic core using openings in a wire guide member to facilitate precise alignment for the creation of a workable inductor.
What is desired is a current mode coupler that weighs less, has a more reliable transformer and core design, and does not require sensitive alignment in order to perform. In addition, a receive-only coupler that only receives data from the current mode data bus is also desired.
The present invention provides a current mode coupler apparatus and corresponding methods suitable for connecting one or more subsystems to a current mode data bus. For example, the current mode coupler disclosed herein is suitable for coupling subsystems typically found in an airplane to a current mode data bus. The present invention provides improvements over conventional connector designs. Specifically, the present invention includes an E-I core arrangement that overcomes the need for design intricacies prevalent in conventional current mode couplers. In addition, the present invention utilizes an inexpensive and more effective circuit board. The present invention eliminates the need for the use of off-the-shelf transformers that have multiple failure modes.
For purposes of summarizing the invention, certain aspects, advantages, and novel features of the invention have been described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any one particular embodiment of the invention. Thus, the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.
One aspect of the present invention relates to a current mode coupler that receives voltage mode doublets, converts the voltage mode doublets into current mode doublets, and transmits the current mode doublets onto a data bus. Additionally, the current mode coupler receives current mode doublets from a data bus and converts the doublets to voltage mode doublets for transmission through a stub cable. The current mode coupler of the present invention includes a stub cable interface, a circuit board communicating with the data bus cable and the stub cable interface, and a data bus interface. The data bus interface includes bus transformers, a ferrite E-core, and a ferrite I-core that encompass the current mode data bus cable when an enclosing lid is in a closed position.
Another aspect of the present invention relates to a current mode coupler that interfaces to a current mode data bus where a ferrite E-core and a ferrite I-core are enclosed by a lid attached to a unitary casing by a hinge. When the enclosing lid is in a closed position, the I-core and the E-core form a magnetic structure that surrounds the data bus cable allowing the transmission and reception of current doublets from the data bus cable. The enclosing lid further includes a spring device located in proximity to the I-core. When the lid is in a closed position, the I-core face and the E-core face contact and the spring mechanism causes a pressurized contact.
A further aspect of the present invention is directed to a current mode coupler that interfaces to a current mode data bus where a ferrite E-core and a ferrite I-core are enclosed by a lid attached to a unitary casing by a sliding mechanism. The sliding mechanism allows for contact between the I-core and E-core faces when it is in the closed position. The lid includes a spring mechanism positioned proximate the I-core such that when the lid is in the closed position, the spring urges the faces of the ferrite cores together.
A yet another aspect of the present invention is directed to a current mode coupler that does not require alignment between the core faces. The use of an E-core/I-core transformer requires only the requisite contact between the E-core faces and the I-core face. No longer are there three E-core surfaces to align with three other E-core surfaces as is typically found in conventional current mode couplers.
A yet further aspect of the present invention is directed to a current mode coupler that is encased in a unitary casing. This eliminates the need for low impedance interconnects between the active and inactive sub-housings, thereby, eliminating weight, component count and manufacturing cost.
One aspect of the present invention is directed to a current mode coupler that includes an enclosing lid and a retention wire. When the enclosing lid is placed in a closed position, the retention wire functions to securely hold the enclosing lid in the closed position.
These and other embodiments of the present invention will also become readily apparent to those skilled in the art from the following detailed description of the embodiments having reference to the attached figures, the invention not being limited to any particular embodiment(s) disclosed.